The present invention relates to a binding for a snow-sport device, such as a short ski, short cross-country ski, snowshoe or snowboard, comprising a base plate which, for holding a boot, has front retention means and rear retention means consisting of a heelpiece mounted slidably on the base plate and a traction strap acting on the heelpiece in order to pull it toward the front retention means.
A binding of this type is known, for a snowshoe, from Patent FR 2 717 093, the content of which is incorporated by reference. In this binding, the rear retention means consist of a shoe block sliding freely over a base plate, this shoe block being pulled forward by a strap attached under the shoe block, and connected to a front cover articulated on a stirrup piece fixed to the front of the plate and constituting a front stop. Connected to the sliding shoe block is a second strap passing over the instep in order to press the heel of the boot onto the base plate. Two actions on two different straps are therefore necessary, one in order to fix the boot longitudinally on the base plate and the other to press the heel of the boot onto the base plate. Moreover, in the absence of a boot, the sliding shoe block can move freely along the base plate and it is consequently impossible to preserve presettings of the position of this shoe block on the base plate.
The object of the invention is to simplify and to improve the operation of fitting the device to a boot and the tightening of a binding of this type and, simultaneously, to obtain presetting of the rear retention means.
The binding according to the invention is defined in that the base plate is equipped with a rack over a portion of its length and in that the heelpiece is equipped, on each side, with a lever articulated at an intermediate point on the heelpiece about an axis transverse to the base plate, the lower arms of these levers being connected to the ends of a small arch which hooks into the rack of the base plate, and the upper arms of the levers being connected to the traction strap which is intended to pass diagonally over the instep of the boot.
One and the same strap pushes the heelpiece forward and presses the heel against the base plate. In the tightened position, the articulations of the lower lever arms on the small arch engaged in the rack of the base plate actually convert into fixed points and the levers then work as second-class levers about these fixed points. The diagonal force exerted by the strap passing over the instep is thus multiplied on the articulation axis of the levers on the heelpiece. The force on the instep may therefore be maintained within reasonable limits, without unpleasant pressure on the instep, while pushing the heelpiece forward to a considerable extent, i.e. excellent holding of the boot in the longitudinal direction. These forces may be modified by adjusting the length of the lever arms.
The dual function of the small arch will also be noted. On the one hand, it makes it possible to preserve presetting of the position of the heelpiece, and, on the other hand, it serves as a support point for the levers of the heelpiece.
When the small arch is engaged in a particular notch of the rack, when no boot is fitted in the device, the heelpiece may be withdrawn until the small arch occupies a position parallel to the plane of the base plate. This easily makes it possible for the heelpiece to travel a distance of the order of 25 mm, which is more than sufficient for easy and comfortable fitting of the device to a boot. When no boot is fitted in the device, the adjustment is preserved and the heelpiece is unable to move freely over the base plate.
The maximum amplitude of the displacement of the points of articulation of the small arch on the levers during rotation of this lever is advantageously greater than the pitch of the rack. The small arch may thus occupy two different positions for one and the same boot size, and continuous adjustment is obtained together with the guarantee of satisfactory tightening.
The front retention means may consist of a simple strap. This will be the case, for example, for a snowboard binding.
The front retention means may consist of a fixed stop providing only longitudinal holding. In this case, the binding comprises intermediate retention means consisting, for example, of a strap.
Generally speaking, the binding according to the invention, which is nonreleasable, is intended for sports devices which do not require such a release capability.